JSFiddle - React, Tailwind, and code Playground

HTML

<div id="html">
  <div id="inner">Simulated page content</div>
</div>

CSS

#html{
	background: url(http://placeimg.com/500/500/animals);background-size: cover;
	/* TRANSITION */
	-webkit-transition: background-image 3s;
	-moz-transition: background-image 3s;
	-o-transition: background-image 3s;
	transition: background-image 3s;
}
#inner{width:100%;height:100vh;background:transparent;}

JavaScript

setTimeout(function(){
		$('#html').css('background-image','url(http://placeimg.com/500/500/nature)');
},2000);